Motor System Disorders

Question 1

What is the basal ganglia composed of?

Answer 1

Substantia nigra pars compacta (SNc)

Striatum

Globus Pallidus

Subthalamic nucleus

Question 2

What does the substantia nigra produce?

Answer 2

It is a source of dopamine in the midbrain

Question 3

Where is the caudate nucleus?

Answer 3

It is C shaped and it lines the lateral ventricle.

Question 4

What makes up the striatum?

Answer 4

Caudate and putamen.

This receives input from the SNc and cortex.

Question 5

What makes makes up the lentiform nucleus?

Answer 5

Putamen and globus pallidus

They are anatomically but not functionally related.

Question 6

How does the basal ganglia communicate with the motor cortex?

Answer 6

Via the thalamus.

Increased thalamic activity causes increases cortical activity and visa versa.

Question 7

What is the normal function of the basal ganglia?

Answer 7

Unclear!

Probable role in reinforcing appropriate movements and removing inappropriate movements.

Direct pathway = reinforce appropriate movements (excitatory).

Indirect pathway = edit out inappropriate movements (inhibitory).

Question 8

What does dopamine do?

Answer 8

Dopamine facilitates movement by exciting the motor cortex. (excites direct pathway by stimulating excitatory D1 receptors on stratal neurones taking part in the direct pathway, inhibits indirect pathway by activating inhibitory D2 receptors on stratal neurones taking part in the indirect pathway.)

Question 9

Do the basal ganglia regulate the ipsilateral or contralateral side?

Answer 9

Ipsilateral motor cortex, so if the SNc os affected unilaterally (rate) there will becontralateral signs due to decussation of the corticospinal tract.

Question 10

What causes the Parkinsonian symptoms?

Answer 10

Caused by degeneration of dopaminergic neurones in SNc.

Therefore, have alsot the dopamine-driven facilitation of movement via both pathways.

Question 11

What are the signs and symptoms of Parkinsons?

Answer 11

Tremor

Rigidity

Bradykinesia

Hypophonia

Decreased facial movements / mask like facies

Micrographia (small handwriting)

Dementia

Depression

Question 12

What is the inheritance pattern of Huntington’s?

Answer 12

Autosomal dominant

Question 13

When does Huntingtons usually start showing symptoms?

Answer 13

Early onset around 30-50 years old

Question 14

What is the early stages of Huntington’s associated with?

Answer 14

Early stages of Huntington’s is associated with loss of inhibitory projections from striatum to GPe.

This leads to hyperkinetic features (increased movements as the brakes have been taken off the thalamus)

Question 15

What are the features of Huntington’s?

Answer 15

Chorea (dance-like movements due to increased motor cortex activation)

Dystonia (uncomfortable contractions of agonists and antagonists simultaneously leading to odd postures caused by over activity in agonist/antagonist muscle circuits and loss of co-ordination between these)

Loss of co-ordination

Cognitive decline and behavioural disturbances (related to role of basal ganglia in higher metabolic functions)

Question 16

What is hemiballismus?

Answer 16

Rare.

Can be caused by damage to sub thalamic nucleus which normally inhibits thalamus via GPi

Can be caused by sub-cortical stroke.

Causes unilateral explosive (ballistic movements)

Question 17

Describe the anatomy of the cerebellum

Answer 17

It is comprised of a midline vermis and two laterally placed ventricles.

It its above the fourth ventricle.

Cerebellar lesions ca cause hydrocephalus.

Question 18

What parts of the cerebellum control what parts of the body?

Answer 18

Vermis = trunk 
Hemispheres = ipsilateral side of the body.

They then communicate with the rest of the CNS via the cerebellar peduncles.

Question 19

Describe what the cerebellar peduncles connect to.

Answer 19

Superior cerebellar peduncle - midbrain

Middle cerebellar peduncle - pons

Inferior cerebellar peduncle - medulla.

Question 20

What are the normal functions of the cerebellum?

Answer 20

Obscure!

Clear role in the sequencing and co-ordination of movements.

Uses sensory information to decide upon the most appropriate movements to perform an action.

Works with basal ganglia which decide most appropriate movements. Cerebellum sequences these movements.

Cerebellum has profuse sensory inputs from proprioceptive neurones and the sensory cortices.

Cerebellum receives sensory input from ipsilateral spinal cord and contralateral sensory cortices. Its output are to the contralateral motor cortex. Hence, ipsilateral signs of cerebellar damage are due to the decussation of corticospinal pathway.

Question 21

What are the signs of cerebellar disease?

Answer 21

DANISH

D - Dysdiadochokinesia

A - Ataxia

N - Nystagmus

I - Intention tremor

S - Slurred speech (dysarthria)

H - Hypotonia